Ok.... assuming that I have to convert my audio, lets draw out the problem into a simple example...

Lets say the audio data is 8-bit signed samples. Instead what I need to play it back in OpenAL is 8-bit unsigned samples.

Would I not be able to do this to convert?

[pascal]var
original_data: ShortInt; // 8-bit signed value
final_data: Byte;

final_data := original_data + 128;[/pascal]

Considering this would equally transfer the place within the range of -128 to 127 over to 0 to 255?

Same, same with 16-bit values only that it's double the range...?